The present invention is related to the field of lubricating oil supply for automatic transmissions of automotive vehicles, and, more particularly, is related to the field of lubricating oil supply in such automatic transmissions, wherein lubricating oil is supplied to a through axial lubricating oil hole formed in a power output shaft of the transmission, and is supplied, via one or more radially extending holes in the power output shaft, to various components of the automatic transmission for lubrication purposes.
In general, in an automatic transmission, lubricating oil is provided by an oil pump driven by a rotating member of the transmission, and this lubricating oil is supplied, through a lubricating oil supply passage provided in part of the transmission case, and through a radially extending lubricating oil supply hole in the power output shaft, to an axially extending through lubricating oil hole which passes along the axis of the power output shaft. From this axial through lubricating oil hole, via one or more radially extending holes in the power output shaft, supply of lubricating oil is provided to various components, such as radial bearings, thrust bearings, planetary gear mechanisms, friction members, bushes, etc., of the automatic transmission, so as to enable their functioning to be maintained over a long period of time. This lubricating oil is usually passed through a lubricating oil cooler mounted at the front of the automotive vehicle, before it is thus supplied.
This lubricating oil supply passage in the automatic transmission case opens, generally, to an internal surface of the part of the transmission case which provides a power output shaft support opening through which the power output shaft projects. Since, inevitably, the inner radial dimension of the power output shaft support opening in the transmission case, and the outer diameter of the portion of the power output shaft which is supported thereby, will be different, thus forming a clearance, there is a possibility of leakage of lubricating oil out from the transmission case through this clearance. In other words, escape of lubricating oil presents a problem. Therefore, it is practiced to mount a lubricating oil seal ring on the output shaft, in a circumferential groove machined generally on the outer surface thereof, so as to intercept such leakage of lubricating oil.
However, the provision of this circumferential groove on the outer surface of the power output shaft reduces its effective cross section, and thereby the strength of the power output shaft is reduced.
There is also a difficulty in the assembly of such an automatic transmission, in that, if the lubricating oil seal ring is mounted directly onto the end of the power output shaft, when the power output shaft is being assembled into the transmission case, this lubricating oil seal ring must be passed through the openings in various transmission components, such as bushes and the like, which have already been assembled into the transmission case, and this runs the risk of damaging either said lubricating oil seal ring or these components themselves. It is very difficult to positively avoid collision between the lubricating oil seal ring and these components.